Congress on Friday sought to turn the tables on former foreign minister Jaswant Singh over his charge that someone in the Prime Miminter's Office during P V Narasimha Rao-led Congress government had been leaking nuclear secrets to the US, by accusing the senior Bharatiya Janata Party leader of "abetting" in the crime.

"If they (those in the BJP) accuse this person of being a spy and treacherous to India or revealing secrets, then by knowing of him and not revealing his identity are they themselves or Jaswant Singh not himself an abettor to the crime?", party spokesman Abhishek Singhvi told reporters.

Noting that the charge had come some 10 years after the Rao government demitted office, he wondered as to what those in the BJP were doing in the matter when they were in power from 1998 to 2004 and are in the opposition since then.

By making the charge after the death of Rao, Jaswant Singh hopes that there was no controversy in the matter, Singhvi said.

The leader of opposition in the Rajya Sabha said he had come to know about it a decade ago, but remained quiet so far as he did not want to sensationalise the issue.

"Yes, there was a person in the PMO. I have evidence, a letter which gives graphic details," Singh told India Today magazine when asked to elaborate on his contention in his book A Call to Honour: In Service of Emergent India that there was a mole in the PMO of the previous Congress government.

Without naming anybody, the leader of the opposition in the Rajya Sabha claimed in his book, "Somebody in the PMO was giving information about India's nuclear programme to the US. It was during the previous Congress regime... We were snooped, we are still being snooped."